Infrared reflection absorption spectroscopy and quartz crystal microbalance, integrated into a one-surface analytical system, and complemented with tapping mode atomic force microscopy, has been used to explore the metal/atmosphere interfacial region under atmospheric pressure conditions. This unique combination of ill situ techniques, all possessing submonolayer sensitivity, has revealed information on the different accelerating roles of ozone (O-3) and nitrogen dioxide (NO2) on the SO2-induced atmospheric corrosion of copper. The formation of reaction products could be followed quantitatively with respect to chemical identity and kinetics. Exposure in SO2-containing humidified air resulted in CuSO3. xH(2)O-like species, formed atop a cuprous oxide, designated Cu2O, all over the copper surface. O-3 introduction resulted in an accelerated mass gain with an increased formation rate of both Cu2O and of CuSO4. xH(2)O all over the surface. NO2 introduction resulted in less mass gain than observed under SO2 and O-3, with no formation of new Cu2O, an initial oxidation of CuSO3. xH(2)O to CuSO4. xH(2)O, and with sulfite oxidation gradually replaced by copper nitrate formation, possibly as CuNO3(OH)(3) The formation rates of the dominating end products, CuSO4. xH(2)O in SO2/O-3 and Cu2NO3(OH)(3) in SO2/NO2 seemed to be limited by the supply of the gaseous constituents.

A novel three-layer anode having the composition Ti/TiHx/Ni-Sb-SnO2 (Ti/TiHx/NATO) was successfully prepared by a spin-coating and pyrolysis process aiming at a long service lifetime and good electrocatalytic properties for ozone formation. The TiHx as an interlayer was produced by electrochemical cathodic reduction of a coated layer of the TiOx on the titanium substrate. Spin coating and thermal decomposition were used to deposit the Sn-Sb-Ni precursor on the surface of the prepared Ti/TiHx electrode. Cyclic and linear scanning voltammetry, Raman spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to reveal the electrode performance and morphology. Results show that the onset potential for the oxygen evolution reaction (OER) of Ti/TiHx /NATO is higher than for Ti/NATO. They also indicate that the service lifetime of the Ti/TiHx/NATO is twice as long as the Ti/NATO at a current density of 50 mA.cm(-2) at room temperature. Electrochemical ozone generation and degradation of the methylene blue were investigated to confirm selectivity and activity of the electrodes. After 5 min electrolysis, a current efficiency for ozone generation of 56% was obtained the electrode with TiHx while 38% was obtained on Ti/NATO under same conditions. The results also confirm that the Ti/TiH x /NATO has a higher kinetic rate constant and decolorization efficiency for removal of the methylene blue compare to the Ti/NATO. The rate constant for the pseudo-first ordered reaction of methylene blue degradation showed high values of 350 x 10(-3) min(-1) for Ti/NATO and 440 x 10(-3) min(-1) for Ti/TiHx/NATO.

A novel three-layer anode having the composition Ti/TiHx/Ni-Sb-SnO2 (Ti/TiHx/NATO) was successfully prepared by a spin-coating and pyrolysis process aiming at a long service lifetime and good electrocatalytic properties for ozone formation. The TiHx as an interlayer was produced by electrochemical cathodic reduction of a coated layer of the TiOx on the titanium substrate. Spin coating and thermal decomposition were used to deposit the Sn-Sb-Ni precursor on the surface of the prepared Ti/TiHx electrode. Cyclic and linear scanning voltammetry, Raman spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to reveal the electrode performance and morphology. Results show that the onset potential for the oxygen evolution reaction (OER) of Ti/TiHx /NATO is higher than for Ti/NATO. They also indicate that the service lifetime of the Ti/TiHx/NATO is twice as long as the Ti/NATO at a current density of 50 mA.cm(-2) at room temperature. Electrochemical ozone generation and degradation of the methylene blue were investigated to confirm selectivity and activity of the electrodes. After 5 min electrolysis, a current efficiency for ozone generation of 56% was obtained the electrode with TiHx while 38% was obtained on Ti/NATO under same conditions. The results also confirm that the Ti/TiH x /NATO has a higher kinetic rate constant and decolorization efficiency for removal of the methylene blue compare to the Ti/NATO. The rate constant for the pseudo-first ordered reaction of methylene blue degradation showed high values of 350 x 10(-3) min(-1) for Ti/NATO and 440 x 10(-3) min(-1) for Ti/TiHx/NATO.

The effect of the electrolyte additive fluoroethylene carbonate (FEC) for Li-ion batteries has been widely discussed in literature in recent years. Here, the additive is studied for the high-voltage cathode LiNi0.5Mn1.5O4 (LNMO) coupled to Li4Ti5O12 (LTO) to specifically study its effect on the cathode side. Electrochemical performance of full cells prepared by using a standard electrolyte (LP40) with different concentrations of FEC (0, 1 and 5 wt%) were compared and the surface of cycled positive electrodes were analyzed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The results show that addition of FEC is generally of limited use for this battery system. Addition of 5 wt% FEC results in relatively poor cycling performance, while the cells with 1 wt% FEC showed similar behavior compared to reference cells prepared without FEC. SEM and XPS analysis did not indicate the formation of thick surface layers on the LNMO cathode, however, an increase in layer thickness with increased FEC content in the electrolyte could be observed. XPS analysis on LTO electrodes showed that the electrode interactions between positive and negative electrodes occurred as Mn and Ni were detected on the surface of LTO already after 1 cycle. (C) The Author(s) 2017. Published by ECS. All rights reserved.

The effect of secondary hardening of tempered AISI 420 martensitic stainless steel on the corrosion behavior in aqueous 0.01 M NaCl has been studied, in-situ, using atomic force microscopy (AFM) to monitor real-time localized corrosion processes. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, and X-ray diffraction analyses confirmed the presence of undissolved and secondary carbides (Cr23C6, Cr7C3, Cr3C2, Cr3C, Cr2C, and CrC) as well as retained austenite, all finely dispersed in the tempered martensitic matrix. Electrochemical measurements, consisted of monitoring of the open-circuit potential vs. time and cyclic polarization in 0.01 M NaCl solution, were performed to evaluate the passivity and its breakdown, and it was seen that initiation sites for localized corrosion were predominantly peripheral sites of carbides. In-situ AFM measurements revealed that there was a sequence for localized corrosion in which the neighboring matrix next to secondary carbides dissolved first, followed by corrosive attack on regions adjacent to undissolved carbides. Tempering at 500◦C reduced the corrosion resistance and the ability to passivate in comparison to tempering at 250◦C.

The corrosion and contact resistances of coated and uncoated stainless steel grades were studied. The coatings studied were PVD CrN and arc discharge deposited Au. The samples were aged in long steady-state experiments using a multisinglecell device. MEAs and exhaust water were analyzed for accumulated iron after measurements. Iron accumulation was measured from MEAs, exhaust water and gas outlet pipes from the cells. The interfacial contact resistances were measured before and after the fuel cell experiments. Low contact resistance was achieved with all coated samples. The main accumulation site of dissolved iron was found to be the MEA and GDLs. A large variation in the corrosion results due to differences in the coating quality was observed. Some coatings with low interfacial contact resistance were found to be prone to corrosion. The CrN coating was also tested in a stack, and it performed well. It was concluded that the multisinglecell is a useful tool for screening different coatings reliably and cost-effectively.

Electrochromic (EC) films of nickel oxide, with and without vanadium, were prepared by reactive dc magnetron sputtering. They were characterized by electrochemical and optical measurements and studied by X-ray photoelectron spectroscopy (PES) using synchrotron radiation. The films were analyzed under as-deposited conditions and after bleaching/coloration by insertion/extraction of protons from a basic solution and ensuing charge stabilization. Optical measurements were consistent with a coloration process due to charge-transfer transitions from Ni2+ to Ni3+ states. The PES measurements showed a higher concentration of Ni3+ in the colored films. Moreover, two peaks were present in the O 1s spectra of the bleached film and pointed to contributions of Ni(OH)(2) and NiO. The changes in the O 1s spectra upon coloration treatment indicate the presence of Ni2O3 in the colored film and necessitated an extension of the conventional model for the mechanism of EC coloration. The model involves not only proton extraction from nickel hydroxide to form nickel oxyhydroxide but also participation of NiO in the coloration process to form Ni2O3.

Silicon p-n diodes formed in the walls of deep pores have been electrically characterized. The pores were electrochemically etched in low-doped n-type silicon substrates, and the entire pore array was doped p(+) by boron diffusion at 1050 degrees C. Two different process flows were investigated to disconnect the p(+) layers from one pore to another. The first consists of removing a few micrometers of silicon at the top of the sample using reactive ion etching after diffusion while the second enables the prevention of doping at the top of the pore walls with an oxide, acting as a barrier during diffusion. Current-voltage and capacitance-voltage characteristics of p-n junctions are presented and related parameters, such as the serial resistance and the ideality factor are discussed. The results show good rectifying behavior of the diodes with a reverse current about four to five decades smaller than the forward current. Measurements with two pores connected in a transistor-like configuration (p(+)/n(-)/p(+)), were also performed. Device simulations were used to examine the device behavior. Finally, our results demonstrate that pores could work as individual detector pixels for moderate reverse voltages, suitable for radiation imaging applications.

Rapid transitions in the response of platinum-based chemical sensors occurring at given hydrogen-oxygen concentration ratios are explained by kinetic phase transitions or switching phenomena on the catalytic metal surface. Below the transition point the response of platinum-insulator silicon carbide devices is small and above the transition it is large. It is found that the critical ratio depends on the operation temperature and the properties of the device. Three different cases are identified, namely, injection-, diffusion-, and reaction-rate-determined transitions. At sufficiently large temperatures the transition is injection limited and occurs at the stoichiometric ratio of hydrogen and oxygen in the gas mixture. The implications of the experimental observations on the applications of chemical sensors with catalytic sensing layers are discussed.

A quasi-realistic aging test of NCA/graphite lithium-ion 18650 cylindrical cells is performed during a long-term low c-rate cycling and using a new protocol for testing and studying the aging. This to emulate a characteristic charge/discharge profile of off-grid PV-battery systems. The cells were partially cycled at four different cut-off voltages and two state of charge ranges (Delta SOC) for 1000 and 700 cycles over 24 months. Differential voltage analysis shows that a combination of loss of active material (LAM) and loss of lithium inventory (LLI) are the causes of capacity loss. Cells cycled with high cut-off voltages and wide Delta SOC (20% to 95%) were severely affected by material degradation and electrode shift. High cut-off voltage and narrow Delta SOC (65% to 95%) caused greater electrode degradation but negligible cell unbalance. Cell impedance is observed to increase in both cells. Cells cycled with middle to low cut-off voltages and narrow Delta SOC (35%-65% and 20% to 50%) had comparable degradation rates to calendar-aged cells. Cycling NCA/graphite cells with low c-rate and high cut-off voltages will degrade the electrode in the same way high c-rate would do. However, low c-rate at low and middle cut-off voltages greatly decrease cell degradation compared to similar conditions at middle to high c-rate, therefore increasing battery lifetime.

The corrosion layer Formed in the contact between the cathode and the current collector is one factor limiting the cathode performance in molten carbonate fuel cells (MCFC). In order to investigate the contribution to the total polarization of the contact resistance, electrochemical experiments were performed in a laboratory-scale fuel cell unit with a specially designed current collector. Two cathode materials, NiO and LiCoO2, were investigated to elucidate the impact of the cathode material on the formed corrosion layer. Polarization measurements as well as electrochemical impedance spectroscopy were used. The method works well for NiO electrodes. However, due to the poor electronic conductivity in the LiCoO2 electrode, the experimental results become difficult to evaluate due to a nonuniform potential distribution. The contact resistance between the cathode and the current collector contributes with a large value to the total cathode polarization. The corrosion layer in case of the LiCoO2 cathode was iron-rich and has a thickness of about 20 mum after 8 weeks operation of the fuel cell. Ln the case of the NiO cathode, a nickel-rich corrosion layer of about 15 mum was formed after 5 weeks operation of the fuel cell.

17. Influence of Grain Boundaries on Dissolution Behavior of a Biomedical CoCrMo Alloy

In this study, preferential sites for metal dissolution during anodic polarization were investigated for a biomedical CoCrMo alloy. As-cast and heat treated materials were compared through a combination of complementary techniques. Scanning Kelvin probe force microscopy mapping suggested the matrix areas adjacent to the carbides to be preferential sites for metal dissolution. By means of in situ electrochemical-optical microscopy it was observed that localized dissolution initiated from the matrix areas adjacent to carbides and grain boundaries in both materials at high anodic potential. By using scanning electron microscopy and transmission electron microscopy/energy dispersive spectroscopy analysis, submicron-sized carbides were found along the grain boundaries, and significant Cr depletion was detected across the grain boundaries for both materials, providing an explanation for the initiation of metal dissolution. A slightly higher metal dissolution was observed for the as-cast sample at high anodic potential, probably due to a more heterogeneous microstructure.

An isothermal two-dimensional liquid phase model for the conservation of mass, momentum, and species in the anode of a direct methanol fuel cell (DMFC) is presented and analyzed. The inherent electrochemistry in the DMFC anode active layer is reduced to boundary conditions via parameter adaption. The model is developed for the case when the geometry aspect ratio is small, and it is shown that, under realistic operating conditions, a reduced model, which nonetheless describes all the essential physics of the full model, can be derived. The significant benefits of this approach are that physical trends become much more apparent than in the full model and that there is considerable reduction in the time required to compute numerical solutions, a fact especially useful for wide-ranging parameter studies. Such a study is then performed in terms of the three nondimensional parameters that emerge from the analysis, and we subsequently interpret our results in terms of the dimensional design and operating parameters. In particular, we highlight their effect on methanol mass transfer in the flow channel and on the current density. The results indicate the relative importance of mass-transfer resistance in both the flow channel and the adjacent porous backing.

A non-isothermal, two-phase model for a polymer electrolyte fuel cell (PEFC) is presented, analyzed, and solved numerically under three different thermal, and two hydrodynamic, modeling assumptions; the consequences of these are then discussed in terms of thermal and water management and cell performance. The study is motivated by recent experimental results that suggest the presence of previously unreported, and thus unmodeled, thermal contact resistances between the components of PEFCs and the discrepancy in the value for the capillary pressure that is used by different authors when modeling the two-phase flow in PEFCs. For the three different thermal assumptions (assuming effective heat conductivities, isothermal flow, and interfacial and bulk conductivites), liquid saturations of around 10% are obtained at the cathode active layer for 1000 mA cm(-2) and a cell voltage of 0.6 V. When lowering the capillary pressure (hydrodynamic assumption), liquid saturations of almost 30% and locally up to 100% are observed at the active layer of the cathode. At this current density and voltage, temperature differences across the cell of around 9 degrees C are predicted. In addition, the effect of varying clamping pressure within the framework of the model is touched upon. The benefits of the scaling analysis conducted here, to predict correctly, prior to numerical computations, important characteristic cell performance quantities such as current density and temperature drop are also highlighted.

An isothermal two-phase ternary mixture model that takes into account conservation of momentum, mass, and species in the anode of a direct methanol fuel cell (DMFC) is presented and analyzed. The slenderness of the anode allows a considerable reduction of the mathematical formulation, without sacrificing the essential physics. The reduced model is then verified and validated against data obtained from an experimental DMFC outfitted with a transparent end plate. Good agreement is achieved. The effect of mass-transfer resistances in the flow field and porous backing are highlighted. The presence of a gas phase is shown to improve the mass transfer of methanol at higher temperatures (>30 degreesC). It is also found that at a temperature of around 30 degreesC, a one-phase model predicts the same current density distribution as a more sophisticated two-phase model. Analysis of the results from the two-phase model, in combination with the experiments, results in a suggestion for an optimal flow field for the liquid-fed DMFC.

Corrosion of copper is a key-issue in the safety assessment of deep geological repositories for spent nuclear fuel utilizing copper coated canisters to isolate the spent nuclear fuel from the surrounding environment. Of particular interest is the radiation induced corrosion attributed to the inherent radioactivity of the spent nuclear fuel. In this work we have studied the radiation induced corrosion of copper in humid air and argon atmospheres. Polished copper cubes were gamma irradiated in the environments mentioned above at ambient temperature. Reference samples, not irradiated but otherwise treated under the exact same conditions as the irradiated samples, were used throughout the study. The oxide layers formed during radiation exposure were studied using cathodic reduction, infrared reflection/absorption spectroscopy, and the surfaces were examined using scanning electron microscopy. When possible, the concentration of copper in solution was measured using inductively coupled plasma atomic emission spectroscopy. The experimental results clearly show that radiation induced corrosion of copper in humid air as well as in humid argon is significantly more extensive than the corresponding process in anaerobic water. This is well in line with the recently proposed mechanism for radiation-induced corrosion of copper in anaerobic water. The very similar behavior of copper irradiated in humid air and in humid argon implies that the radiolytically formed HNO3 in the case of humid air has negligible impact on the radiation-induced corrosion compared to the radiolytically formed hydroxyl radical.

The cycle life of LiNi1/3Co1/3Mn1/3O2 (NMC) based cells are significantly influenced by the choice of the negative electrode. Electrochemical testing and post mortem surface analysis are here used to investigate NMC electrodes cycled vs. either Li-metal, graphite or Li4Ti5O12 (LTO) as negative electrodes. While NMC-LTO and NMC-graphite cells show small capacity fading over 200 cycles, NMC-Li-metal cell suffers from rapid capacity fading accompanied with an increased voltage hysteresis despite the almost unlimited access of lithium. X-ray absorption near edge structure (XANES) results show that no structural degradation occurs on the positive electrode even after >200 cycles, however, X-ray photoelectron spectroscopy (XPS) results shows that the composition of the surface layer formed on the NMC cathode in the NMC-Li-metal cell is largely different from that of the other NMC cathodes (cycled in the NMC-graphite or NMC-LTO cells). Furthermore, it is shown that the surface layer thickness on NMC increases with the number of cycles, caused by continuous electrolyte degradation products formed at the Li-metal negative electrode and then transferred to NMC positive electrode.

A laboratory study of the effect of CO2 and NaCl on the atmospheric corrosion of aluminum is reported. The samples were exposed to pure air with 95% relative humidity and the concentration of CO2 was <1 and 350 ppm, respectively. Sodium chloride was added before exposure (0, 14, and 70 g/cm(2)). The main result is that the NaCl-induced atmospheric corrosion of aluminum is about 10 to 20 times faster in CO2-free humid air compared to air containing ambient levels of CO2. It is suggested that the rapid corrosion of aluminum coated with NaCl in humid CO2-free air is connected to high-pH areas in the surface electrolyte that develop due to the cathodic reduction of oxygen. The anodic dissolution of aluminum is known to be enhanced by high pH. The unexpected corrosion-inhibitive effect of CO2 is explained by the neutralization of the surface electrolyte. In the absence of CO2, bayerite, Al(OH)(3), forms. Only minute amounts of carbonate were found on the surface after exposure to CO2-containing air.

24. A Model for Mass Transport of Molten Alkali Carbonate Mixtures Applied to the MCFC

A one-dimensional model based on the Stefan-Maxwell formulation for mass transfer of the main components of a binary molten carbonate electrolyte, including all of the nonidealities, was formulated and applied to the molten carbonate fuel cell (MCFC). The Stefan-Maxwell diffusion coefficients were determined from literature transport data; still, a narrow parameter window in electrolyte composition and temperature had to be used to keep the integrity of the fits. The model for calculation of the electrolyte composition was combined with equations describing the current distribution in the electrodes and the electrolyte. The calculated results of the electrolyte composition changes show that they depend predominantly on the current density and the total electrolyte filling degree. It was also concluded that the electrolyte composition changes are less then two percent for Li/K and five percent for Li/Na. This model demonstrates how experimental data measured at equilibrium conditions may be used to determine Stefan-Maxwell diffusion coefficients and then applied to a transport model for the electrolyte, in this case an MCFC.

Experimental data of the total cell reaction resistance as a function of the total electrolyte filling degree was measured to investigate how more electrolyte initially may be added to get as long a cell lifetime as possible. The reaction resistance of each electrode was also measured using two gas compositions and various total electrolyte filling degrees. A theoretical model for the distribution of electrolyte between the anode and the cathode as a function of the total electrolyte filling degree was used to compare the experimental data in this study with data from a symmetrical cell setup. The model takes into account the electrode pore-size distributions and considers two cases for the contact angle between the electrode and the electrolyte for the anode: a zero wetting angle (fully wetted) or reported experimental values for the wetting angle on pure Ni. It was concluded that after the cathode initially has been sufficiently filled with electrolyte the anode pores have to be smaller than the remaining ones of the cathode to allow having the anode act as a reservoir to prolong cell lifetime. The results from the experimental data and the theoretical model for electrolyte distribution were compared with results from a symmetrical setup.

The potential-dependent optical-absorption spectroscopy of nanostructured TiO2 (anatase) is most fully accounted for by two processes, band-filling and intercalation. Under weak-accumulation conditions, occupation of surface and conduction-band states by electrons dominates with the accumulated charge being compensated by adsorbed protons or cations. Under strong-accumulation conditions, however, intercalation of protons or cations may take place with a fraction of the accumulated electrons being localized at Ti-IV sites.

27. Impedance as a Tool for Investigating Aging in Lithium-Ion Porous Electrodes

High-power positive LixNi0.8Co0.15Al0.05O2 composite porous electrodes are known to be the main source of impedance increase in batteries based on GEN2 chemistry. The impedance of positive electrodes, both fresh and harvested from coin cells aged in an accelerated EUCAR hybrid electric vehicle lifetime matrix, was measured in a three-electrode setup and the results fitted with a physically based impedance model. A methodology for fitting the impedance data, including an optimization strategy incorporating a global genetic routine, was used to fit either fresh or aged positive electrodes simultaneously at different states of charge down to 0.5 mHz. The fresh electrodes had an exchange current density of approximately 1.0 A m(-2), a solid-phase diffusion coefficient of approximately 1.4 x 10(-1)5 m(2) s(-1), and a log-normal active particle size distribution with a mean radius of 0.25 mu m. Aged electrode impedance results were shown to be highly dependent on both the electrode state of charge and the pressure applied to the electrode surface. An aging scenario incorporating loss of active particles, coupled with an increase both in the local contact resistance between the active material and the conductive carbon and the resistance of a layer on the current collector, was shown to be adequate in describing the measured aged electrode impedance behavior.

Numerical modeling is becoming an integral part of all research and development within the field of electrolytic systems. A numerical model that calculates the current density distribution and concentration profiles of a chlorate cell is presented here, The results are shown as functions of electrolyte velocity and exchange current density. The model takes into account the three transport mechanisms; diffusion, migration, and convection by considering the development of the flow velocity vector through the channel. It was seen that the developing velocity profile influences the concentration overpotentials, which in turn influences current density distributions. Results from the model show that the total current density decreased along the length of the anode, and that this distribution varied more at lower velocities. In addition, it was seen that migration contributes significantly to species transport, even within the diffusion layer. Finally, the model indicates that the hypochlorite ion is the main participant in the principal side reaction producing oxygen, and not the hypochlorous acid molecule. The results are useful as they increase knowledge of the chlorate process, and can be used to simulate future systems with a wide range of varying parameters such as cell geometry, flow, electrolyte composition, and electrode materials. The aim of the model is to use it as a tool for identifying the sources that contribute to the overpotential in the cell. This article concentrates on the concentration overpotential, which is one of the phenomena that can actually be influenced,

The performance of lithium-ion batteries (LIBs) comprising SnO2 electrodes and an ionic liquid (IL) based electrolyte, i.e., 0.5 MLiTFSI in Pip14TFSI, has been studied at room temperature (i.e., 22◦C) and 80◦C. While the high viscosity and low conductivity ofthe electrolyte resulted in high overpotentials and low capacities at room temperature, the SnO2 performance at 80◦C was found to beanalogous to that seen at room temperature using a standard LP40 electrolyte (i.e., 1MLiPF6 dissolved in 1:1 ethylene carbonate anddiethyl carbonate). Significant reduction of the IL was, however, found at 80◦C, which resulted in low coulombic efficiencies duringthe first 20 cycles, most likely due to a growing SEI layer and the formation of soluble IL reduction products. X-ray photoelectronspectroscopy studies of the cycled SnO2 electrodes indicated the presence of an at least 10 nm thick solid electrolyte interphase (SEI)layer composed of inorganic components such as lithium fluoride, sulfates, and nitrides as well as organic species containing C-H,C-F and C-N bonds.

The FeCrAlRE (where RE is reactive element) alloy Kanthal AF was exposed isothermally at 600 and 800°C for 72 h in dry O2 and in O2 with 10 vol % H2O. The mass gains were 3–5 times higher at the higher temperature. The presence of water vapor increased the oxidation rate at 800°C, while no significant effect was observed at 600°C. A thin two-layered oxide formed at 600°C: an outer (Fe,Cr)2O3 corundum-type oxide, containing some Al, and an inner, probably amorphous, Al-rich oxide. At 800°C a two-layered oxide formed in both environments. The inner layer consisted of inward grown a-Al2O3. In dry O2 the originally formed outward grown g-Al2O3 had transformed to a-Al2O3 after 72 h. Water vapor stabilized the outward grown g-Al2O3 and hence no transformation occurred after 72 h in humid environment. RE-rich oxide particles with varying composition (Y, Zr, and Ti) were distributed in the base oxide at both temperatures and in both environments. The RE-rich particles were separated from the alloy substrate by a layer of Al-rich oxide. At 800°C the Y-rich RE particles were surrounded by thick oxide patches in both dry and humid O2.

Corrosion of steel in concrete has resulted in shorter service life of concrete constructions and it may also cause serious safety accident. Chloride attack and carbonation of the concrete are two of the most crucial trigger factors for the initiation of corrosion. In order to protect the reinforced steel in concrete from corrosion, in this work, a composite inhibitor of layered double hydroxides (LDHs) intercalated with organic phthalates (PTL) and hydroxide ions (MgAl-LDHs-OH-PTL) were synthesized by calcination-reconstruction methods in ambient atmosphere. The structure, composition and morphology of the prepared MgAl-LDHs-OH-PTL were obtained by X-ray diffraction, Fourier transform infrared spectroscopy and Scanning Electron Microscopy, respectively. The electrochemical measurements indicated that the inhibition efficiency of MgAl-LDHs-OH-PTL for carbon steel in the simulated carbonated concrete pore (SCCP) solutions reached more than 90% when its concentration was 20 g/L. It was found that the MgAl-LDHs-OH-PTL possessed multifunctional protection roles for the carbon steel in concrete, which mainly included decrease of aggressive Cl-ions, increase of the pH of SCCP solutions and release of PTL anions to the solution gradually. The work indicated the promising potential of LDHs compounds as effective multifunctional inhibitors in the field of corrosion protection of reinforced concrete.

This work provides insight into the fabrication of ZnAl layered double hydroxides (LDHs) intercalated with organic phthalates (PTL) and their corrosion protection of steel reinforced concrete. The structure, composition and morphology of the LDH products prepared by various methods were systematically characterized to find out the relationship of preparation-structure-properties. The ZnAl-LDH-PTL prepared by co-precipitation method presented the best performance of corrosion protection due to its good crystallinity. The corrosion protection mechanism of LDH for steel in concrete system was also discussed.

Alkaline iron electrodes present some challenges for use in secondary batteries that are associated with low coulombic efficiency and discharge utilization. Low coulombic efficiency is correlated to the hydrogen evolution reaction that takes place during charge. In this work, we demonstrate rechargeable alkaline iron electrodes with significant capacity retention over 150 cycles with high efficiency by suppressing the hydrogen evolution with stannate. Adding stannate to the alkaline electrolyte when cycling the iron electrode drastically changes the electrochemistry. The additive brings on two advantageous attributes for the iron electrode: increased hydrogen evolution overpotential, and a flat and prolonged discharge curve at typical battery operation. These attributes were provided by a novel intermediate phase that was detected from in situ neutron diffraction measurements. This phase was only detected in situ while it decomposed ex situ, and indicated a solid solution constituted by some of the elements present in the electrode.

The influence of surface adsorption of benzotriazole (BTAH) and of chloride ions (Cl-) on the kinetics of copper electrodeposition/dissolution in copper sulfate solutions and on copper deposit characteristics have been investigated using electrochemical quartz crystal microbalance (EQCM) combined with cyclic voltammetry (CV). The addition of BTAH alone increases the overpotential of copper deposition, whereas a Cu(I)BTA complex forms at potentials higher than 0.08 V (vs. SCE) accompanied with the occurrence of copper anodic dissolution. With simultaneous addition of BTAH and Cl-, surface adsorption of Cl- competes with that of BTAH during the initial stage of copper nucleation. Different cuprous reaction intermediates form in the examined potential range -0.4 to 0.3 V (vs. SCE), which partly eliminate the favorable effect of BTAH on the deposited copper. A BTAH-containing adsorbed layer formed on the matte side of electrodeposited copper film in the presence of BTAH with or without Cl-, exhibiting a barrier surface property and an improved corrosion resistance compared with the copper film electrodeposited in the electrolyte without addition of BTAH.

Application of protective coatings on metals may involve a thermal treatment process. In this study, the effect of thermal treatment up to 200 degrees C on the corrosion protection was investigated for nanocomposite films composed of mussel adhesive protein (MAP), CeO2 nanoparticles and Na2HPO4 deposited on carbon steel. The morphology and microstructure of the pre-formed nanocomposite film were characterized by scanning electron microscopy/energy dispersive spectroscopy and atomic force microscopy (AFM). The changes in the chemical structure of the nanocomposite film due to the thermal treatment were investigated by infrared reflection absorption spectroscopy. The corrosion protection of the unheated and heated nanocomposite films on carbon steel was evaluated by electrochemical impedance spectroscopy and details of the corrosion process were elucidated by in-situ AFM measurements in 0.1 M NaCl solution. The results show a certain increase in the corrosion protection with time of the nanocomposite film for carbon steel. The analyses reveal that thermal treatment leads to a reduction of water molecules in the nanocomposite film, and an enhanced cross-linking and cohesion of the film due to oxidation of catechols to o-quinones. As a result, the film becomes more compact and gives improved corrosion protection for carbon steel.

Application of protective coatings on metals may involve a thermal treatment process. In this study, the effect of thermal treatment up to 200?C on the corrosion protection was investigated for nanocomposite films composed of mussel adhesive protein (MAP), CeO2 nanoparticles and Na2HPO4 deposited on carbon steel. The morphology and microstructure of the pre-formed nanocomposite film were characterized by scanning electron microscopy/energy dispersive spectroscopy and atomic force microscopy (AFM). The changes in the chemical structure of the nanocomposite film due to the thermal treatment were investigated by infrared reflection absorption spectroscopy. The corrosion protection of the unheated and heated nanocomposite films on carbon steel was evaluated by electrochemical impedance spectroscopy and details of the corrosion process were elucidated by in-situ AFM measurements in 0.1 M NaCl solution. The results show a certain increase in the corrosion protection with time of the nanocomposite film for carbon steel. The analyses reveal that thermal treatment leads to a reduction of water molecules in the nanocomposite film, and an enhanced cross-linking and cohesion of the film due to oxidation of catechols to o-quinones. As a result, the film becomes more compact and gives improved corrosion protection for carbon steel.

A nanocomposite film composed of mussel adhesive protein (MAP) and CeO2 nanoparticles has been explored as a 'green' alternative for corrosion protection of carbon steel. In this work, the nanocomposite film of sub-micron thickness was deposited on carbon steel surface by one-step-dipping method. The film was characterized by using scanning electron microscope/energy dispersive spectroscopy and atomic force microscope (AFM). The measurements of scanning reference electrode technique and in-situ AFM were performed to investigate the initial localized corrosion process at defects and self-healing ability of the nanocomposite film. The results demonstrate that the nanocomposite film possesses a certain self-healing ability and provides excellent corrosion protection for carbon steel in neutral 0.1 M NaCl solution. The self-healing ability is attributed to the functional group (catechol) of the MAP, and the healing process is explained by the fact that Fe ions released from the surface defects promote the formation of Fe-catecholato complexes in the nanocomposite film, which retards the localized corrosion at these defects.

The initial SO2-induced atmospheric corrosion of copper deposited with NaCl has been examined with Fourier transform infrared microspectroscopy under in situ and ex situ conditions in order to reveal the spatial distribution of reaction products. The oxidation of S(IV) turns out to be fast at the area of the NaCl-containing electrolyte droplet, and both sulfate (SO42-) and dithionate (S2O62-) ions form. A copper-catalyzed reaction route for the sulfite oxidation has been suggested, which includes the formation of a Cu(II)-sulfito complex as an important step. The presence of gaseous oxidants such as NO2 and O-3 has previously been considered as an important prerequisite for the oxidation of sulfite on copper. The results obtained here suggest that the formation of local electrochemical cells induced by deposited NaCl particles could be another important route for S(IV) oxidation to sulfate formation. SO2 was found to promote the formation of less soluble paratacamite [Cu-2(OH)(3)Cl] and nantokite (CuCl), which may slow down the atmospheric corrosion rate of copper.

The effect of carbon dioxide (CO2) on the NaCl-induced atmospheric corrosion of copper was studied using in situ Fourier transform infrared microspectroscopy, in situ scanning Kelvin probe, and scanning electron microscopy/energy-dispersive analysis by X-ray. The copper surface was contaminated with a single NaCl particle and then exposed to 80 +/- 2% relative humidity clean humidified air with two concentrations of CO2 (< 5 and 350 ppm). After formation of an electrolyte droplet secondary spreading of electrolyte from the peripherical parts of the droplet was observed. The secondary spreading effect, which was much larger at < 5 ppm CO2 than at 350 ppm, was a consequence of the formation of a galvanic element between a local cathode outside the edge of the droplet and an anode in the droplet. This lead to alkaline conditions in the secondary spreading area and transport of Na+ ions to the local cathode. The large secondary spreading at low CO2 concentration was possible due to lowering of the surface tension of the electrolyte/metal oxide interface at the peripheral parts of the droplet. Carbonate formation lowered the pH when the CO2 concentration was 350 ppm and resulted in a decrease of the pH and inhibition of the secondary spreading.

The effect of carbon dioxide (CO2) on sodium chloride (NaCl) induced atmospheric corrosion of copper was studied in laboratory exposures using microgravimetry, ion chromatography, Fourier transform infrared spectroscopy, and scanning electron microscopy with X-ray microanalysis. With lower amount of NaCl particles on the copper surface (< 15 mu g/cm(2)), the corrosion rate was higher with < 1 ppm CO2 than with 350 ppm CO2, and for higher amount of NaCl (> 15 mu g/cm(2)), the corrosion was higher with 350 ppm CO2. With lower amount of NaCl and low CO2 concentration, a secondary spreading of electrolyte occurred from the droplets that formed at the particle clusters. This led to a larger effective cathodic area and a higher corrosion rate. However, at higher surface concentration of NaCl a spatial interaction effect between the local corrosion sites counteracted the increase in the corrosion rate due to overlap of the cathodic areas from the particles. Another factor, which influenced the corrosion process, was the effect of CO2 on the pH of the surface electrolyte. Higher pH (< 1 ppm CO2 concentration) increased the formation of CuO, which improved the corrosion resistance of the corrosion product layer but hindered the formation of insoluble CuCl, whereby more soluble chloride ions were available for triggering localized corrosion and accelerating the initial atmospheric corrosion of copper. Hence, the overall influence of CO2 and NaCl depends on at least three identified mechanisms.

This work aims to address two major roadblocks in the development of lithium-sulfur (Li-S) batteries: the inefficient deposition of Li on the metallic Li electrode and the parasitic "polysulfide redox shuttle". These roadblocks are here approached, respectively, by the combination of a cellulose separator with a cathode-facing conductive porous carbon interlayer, based on their previously reported individual benefits. Both approaches result in significant improvements in cycle life in test cells with positive electrodes with practically relevant specifications. Despite the substantially prolonged cycle life, the combination of the interlayer and cellulose separator generates an increase in polysulfide shuttle current, leading to greatly reduced Coulombic efficiency. Based on XPS analyses, the latter is ascribed to a change in the composition of the solid electrolyte interphase (SEI) on the Li electrode. At the same time, the rate of electrolyte decomposition is found to be lower in cells with cellulose-based separators, which corroborates the observation of longer cycle life. These seemingly contradictory and counterintuitive observations demonstrate the complicated interactions between the cell components in the Li-S system and how strategies aiming to mitigate one unwanted process may exacerbate another. This study demonstrates the value of a holistic approach to the development of Li-S chemistry.

In this work the anodic reactions taking place on a dimensionally stable anode (DSA) in chlorate electrolyte have been investigated. Rotating disk electrodes were made from commercial RuO2-catalyzed DSAs and studied in steady-state polarization measurements, mainly IR-corrected polarization curves. Effects of varying pH and electrolyte concentrations of chloride, chlorate, chromium(VI), hypochlorite (ClO- + ClOH) as well as mass transport were studied. The kinetics for the chlorine evolution reaction, with a Tafel slope of 40 mV/decade of current, was not dependent on pH in the region 2-8, at potentials lower than 1.2 V vs. Ag/AgCl. The slope of the polarization curves increased at about 1.2 V vs. Ag/AgCl, a pH-dependent bend not due to mass-transport limitations in the electrolyte. At a pH of 6.5, typical for the chlorate process, oxygen evolution is an important side reaction favored by the dichromate buffer and by increased mass transport, both keeping down the pH at the anode. In the chlorine evolution region the potentials increased when adding Cr(VI) to the electrolyte, whereas no major effect was seen from additions of NaClO. (C) 2002 The Electrochemical Society.

Thispaper presents a steady-state model of the feed compartment ofan electropermutation cell, used for nitrate removal, with ion exchangetextiles incorporated as a conducting spacer. In the model theion-exchange textile is treated as a porous medium and volumeaveraging is applied to obtain a macrohomogeneous two-phase model. Theion-exchange between the two phases is modeled assuming that therate-determining step is the mass-transfer resistance on the liquid sideof the phase interface. Analysis of the model equations revealsappropriate simplifications. The influence of the governing dimensionless numbers isinvestigated through simulations based on the model.

Water with nitrate concentrations above 100 ppm has been treated with continuous electropermutation which partially substitutes the nitrate with chloride. The performance of a textile anion exchanger as conducting spacer in the feed compartment of an electropermutation cell was investigated. Experiments with and without textile are compared and the influence of the textile is discussed. The process could, using the textile, successfully treat feed water with 105 ppm nitrate to produce a water with less than 25 ppm nitrate. The importance of establishing a good contact between the membranes and the textile spacer was pointed out. The experimental results were compared to model predictions and a good agreement was found.

A recently reported promising cathode material for solid-oxide fuel cells (SOFCs), namely, BaxSr1-xCoyFe1-yO3-delta (BSCF) is fabricated in nanocrystalline form by a chemical alloying approach. The approach is comprised of solution chemical synthesis of a precursor and its thermochemical processing toward the desired phase. All the constituent elements, Ba, Sr, Co, and Fe, were coprecipitated from an aqueous solution of their salts to produce a precursor with a well-defined composition, fine particle size, high homogeneity, and high reactivity. After calcining and sintering at 1000 degrees C, the individual oxides were alloyed into nanostructured perovskite (with x=0.5 and y=0.2) Ba0.5Sr0.5Co0.2Fe0.8O3 of high purity. Spark plasma sintering was used for compaction to preserve the material's nanostructure, and sintered compacts demonstrated a significant increase in electrical conductivity values at temperatures up to 900 degrees C, compared to the earlier reports. The measured conductivity values are sufficiently high for cathode applications with a maximum of about 63 S cm(-1) at 430 degrees C in air and 25 S cm(-1) at 375 degrees C in N-2, respectively. These values are about twice as high as conventional BSCF mainly due to the reduction in interfacial resistance, implying a high promise for nanoengineered BSCF as cathode material at low or intermediate-temperature SOFCs.

An integrated atomic force microscopy/scanning electrochemical microscopy (AFM/SECM) system was developed as an in situ local electrochemical probing technique. It consists of a dual-mode probe acting as an AFM cantilever and SECM microelectrode to simultaneously obtain the topography and electrochemical current map of the same area. Two types of probes with different geometries were used. The scan velocity and concentration profile of the redox mediator during the scan were simulated, using the equations of convection-diffusion mass transport coupled with continuity and momentum in three dimensions under steady-state and transient conditions. The temporal and spatial resolutions of the probes were investigated. It was found that, during a normal scan rate (around 1 Hz), the effect of convective transport is negligible and the SECM lateral resolution depends on the geometrical parameters. With favorable geometry, a probe with a Pt microelectrode of 1 mu m diameter can distinguish two active sites with a distance of at least 3-4 mu m. The paper also reports experiments for characterization and calibration of the AFM/SECM system. Concurrent AFM and SECM images obtained on a gold band calibration sample verify the high-resolution capability of the SECM of one or a few micrometers with optimized conditions.